Sweetening of hydrocarbons containing mercaptans and/or mercaptides with a chelate and oxygen



United States Patent SWEETENING OF HYDRQCARBONS CONTAINING MERCAPTANS AND/0R MERCAPTIDES WITH A CHELATE AND OXYGEN Joseph Quiquerez, Gonfreville-LOrcher, and Edouard Weisang, Le Havre, France, assignors to Socit Anonyme dite: Compagnie Francaise de RafIinage, Paris, France, a corporation of France No Drawing. Application May 7, 1958 Serial No. 733,506

Claims priority, application France May 10, 1957 6 Claims. (Cl. 208-206) The present invention relates to the treatment of hydrocarbons and mixtures of hydrocarbons containing mercaptans and/or mercaptides, in which these compounds are converted into disulfides.

It is known that it is possible to effect sweetening of petroleum-type hydrocarbons, or of their distillation fractions, by oxidation with oxygen or any gaseous mixture containing oxygen, of the mercaptans and/ or mercaptides contained therein to disulfides, in the presence of chelate organo-metallic compounds, obtained by condensation of an iminophenol and a metal of group VIII of the periodic system, or of suitable compounds to form the chelate compound in situ.

In United States patent specification No. 2,659,691 and in the applications Serial No. 340,918 of March 6, 1953, now US. Patent No. 2,823,173, Serial No. 385,274 of October 9, 1953, now abandoned, and Serial No. 411,256 of February 18, 1954, there are described processes for sweetening petroleum fractions, and various preferred embodiments of these processes.

It has, however, been found by the applicants that the direct application of such a process under general conditions may lead to the occurrence of secondary reactions, which are inconvenient and limit the economic advantage of the process. In fact, on oxidation of the mercaptans and/or mercaptides, it is possible that the degree of oxidation corresponding to the formation of the disulfides may be exceeded and other oxidation products may be formed; these products, although present in small quantities, nevertheless have the disadvantage of being sufficiently unstable to decompose, in turn, under normal storage conditions, for example, into various products having an acid reaction and causing, inter alia, the formation of gums, reduction of the induction period of the petroleum fractions, regeneration of small quantities of mercaptans and so on.

This invention relates to a method of oxidizing mercaptans and/or mercaptides to disulfides, by the action of oxygen or any gaseous mixture consisting essentially of oxygen, in the presence of chelate organo-metallic compounds, obtained by condensation of an iminophenol and a metal of group VIII-or of suitable compounds to form the chelate compound in situ-under determined conditions of temperature and pressure.

Various manners of performance and improvements characteristic of the present invention will be explained in the following description.

It has been found that it is possible to avoid the development of secondary reactions during the oxidation of mercaptans and/or mercaptides to disulfides, and to limit, in fact prevent, in this way the formation of oxidation products other than disulfides, by working at a temperature greater than the ambient temperature and of about 30 C. or more, and at atmospheric pressure.

Moreover, the present invention permits a very considerable increase of the speed of oxidation of the mer- Patented .Dec. 22, 1959 ICC captans and/or mercaptides to disulfides, that is, a re; duction in the time required for attaining sweetening of the sour petroleum fractions by the action of atmospheric oxygen in the presence of chelate organo-metallic compounds or of compounds suitable for forming them in situ.

Another considerable advantage of the method according to the invention is to effect substantial economies in the amounts used of the chelate organo-metallic compounds, or of compounds suitable for forming them in situ, while enablingsweetening of the treated products to be effected at speeds of reaction that are satisfactory from the industrial viewpoint.

Specific embodiments of the invention will now be described by way of example.

EXAMPLE 1 In this example, specially intended to show that the method according to the invention limits, or rather prevents, the formation of compounds more oxidized than the disulfides, a known mercaptantert.-butyl mercap tan-is oxidized in solution in a defined hydrocarbon, namely benzene.

Four l-litre samples of benzene, containing 0.410 g. of sulfur in the form of tert.-buty1 mercaptan, are treated at atmospheric pressure with pure oxygen in the presence of 0.49 ml. of a cresol solution containing 41 mg. of bis (disalicylal-ethylenediimine)- .-aquodicobalt and 41 mg. of lead, in the form of cresolate, at temperatures of 15 C., 25 C., 35 C. and 45 C.

The results, shown in Table I, indicate that, when the method is performed at a temperature greater than ambient temperature, the amount of oxygen consumed is hardly different from the theoretical, corresponding to the oxidation of mercaptans into disulfiides: namely, two atoms of sulfur for one atom of oxygen (i.e. 820:2).

On the other hand, at low temperature, this consumption becomes much more considerable and very considerably exceeds the theoretical value.

As stated hereinabove, one advantage of the method forming the subject of the invention is the avoidance of the formation of secondary reactions and, in particular, of those liable to lead to substantial reductions of the induction periods (stability to oxidation) of the fractions treated.

Thus, for example, two samples (1) and (2) of petrols having the following characteristics:

Petrol (1):

Density at 15 C. 0.720. Boiling range 30 to 180 C. SRSH In], Induction period 419.

Petrol (2):

Density at 15 C 0.715. Boiling range 34 to 148 C. SRSH g. pe1' ml. Induction period 320.

made sweet by treatment with a cresol solution containing 7 percent by weight of the chelate compound-bis (disalicylal-ethylenediimine)- .t-aquodicobaltand 7 per- Temperature C.) 15 35. 45 60 15 I v 7 2,918,426 V i 3 4 7 cent by weight of lead, in the form of cresolate, at This table gives the sulfur contents, in the form of temperatures of 10 C., +15 C. and +35 C., gave mercaptans and in g. per 100 ml., depending on the reacthe induction periods indicated in Table 2. tion time, the reaction temperature and the ratio:

Table 2 E3? 1 5, 1/7 and 1 Induction Induction used.

period for period for petrol (1) petrol (2) e p u e EXAMPLE 4 To twelve samples of a parafiin originating from g8 10 Kuwait and having the following characteristics: 644 Density at c 0.8025.

, Boilin ran e 200 t 247 C. Examples 3 and 4 hereinbelow, which are llkewlse no SRSH i f (1003 g per 100 mL limitative, have the object of illustrating first the increase in the speed of oxidation of the mcrcaptans and/or mer- 15 ther? is fi added a 2 1 Solutlon contammg 1 8- captides to disulfides; namely for given ratios of chelate of dlsahcylal'QthYIemPdUmme P 100 and then a organometanic compounds or suitable compounds f second benzene solution containing 0.1 g. of cobalt and 'forming the chelate compound in situ-to the quantity of f P 100 the form of naphthenates; lf i h f f mercaptans, contained in the frac the quant1t1es of these solutions added are in the stoichitions treated. They further illustrate that, by means of Ometric ratio corresponding to bis(disalicylal'ethylenedithe process forming the subject of the invention, it is )-M- q and the Samples are then treated possible to obtain a determined result-for example, under the working conditions given in Table 4, in which the sweetness of the fractions treatedin a definite time, the results are grouped.

Table 4 Time (hours) 1 2 Temperature C.) 15 60 15 35 45 60 0. 036 0. 0048 0. 0016 0. 0011 0.0012 0. 0032 0. 0008 0.0008 0. 0008 Ratio of chelate/SRsH 0. 026 0.0056 0.0025 0. 0016 0.0016 0. 0047 0. 0008 0. 0010 0.0012 0. 018 0. 0072 0. 0040 0. 0032 0. 0032 0. 0053 0. 0016 0. 002 0.0024

Time (hours) 6 22 Temperature C.) 15 35 45 60 15 35 45 60 0.036 0. 0024 0.0004 0.0004 0.0006 0.0018 1 D.S. D.S. traces Ratio of chelate/Snsa 0. 026 0. 0039 0. 0004 0. 0008 0.0010 0.001 D.S. D.S. 0.0008 0. 018 0. 0043 0. 0012 0.0016 0.0020 0.0016 0. 0004 0.0010 0. 0016 l D.S.=Doctor Sweet.

and with a considerable saving in the amounts of catalyst This table gives the sulfur contents, in the form of required. 46 mercaptans, and in g. per 100 ml., depending on the re- EXAMPLE 3 action time, the reaction temperature and the ratio:

Twelve identical samples of a light petrol originating cobalt from Iraq and having the following characteristics: S (0036 0026 and 0'018) Density at 15 C. 0.697. used. Boiling range 34 to 147 C. 50 The results in Tables 3 and 4 clearly show the favour- S 0.014 g. per 100 ml. able influence of an increase of temperature on the speed of oxidation of the mercaptans and/or mercaptides to disulfides.

Moreover, taking into account the time Within which it is desired to effect the operation and the rate of conversion of mercaptans and/or mercaptides to disulfides are treated with a cresol solution containing 7 percent by weight of the chelate compoundbis(disalicylalethylenediimine)-p.-aquodicobalt-and 7 percent by weight of lead, in the form of cresolate, as will be apparent from Table 3, in which the results obtained are grouped.

Table 3 Time (hours) 1 2 1/5 0.005 0.002 0.0015 0.003 0.0005 0.0005 0.0005 Ratio of ehelate/Snsn 0 002 7 Time (hours) 6 24 Temperature C.) 15 35 45 60 15 35 45 60 1/5 0. 002 17.8. D.S. D.S. 0.0015 D.S. D.S. D.S. Ratio 01 ehelatelsnsn 1/7 0. 000 0. 001 0. 00065 0. 0005 0. 0055 0. 0005 D.S. D.S. 1/10 0. 007 0. 002 0.001 0.004 0. 006 0.001 D.S. 0. 002

1 1),S.="Doetor Sweet."

that it is desired to obtain, it is easy to choose the temperature at which it is necessary to perform the process to use the minimum quantity of chelate; it will be seen that an increase in the temperature permits considerably smaller quantities of chelate to be used.

While this invention has been described and exemplified in terms of its preferred embodiments, those skilled in the art will appreciate that modifications can be made without departing from the scope of the invention as defined in the appended claims.

We claim:

1. A process for oxidizing a member of the group consisting of mercaptans and mercaptides to disulfides in which the oxidation is effected by the action of oxygen, at a temperature of about 30 C. at least and at atmospheric pressure, in the presence of chelate organo-metallic compounds.

2. A process for oxidizing a member of the group consisting of mercaptans and mercaptides to disulfides, in which the oxidation is effected by the action of a gas containing oxygen, at a temperature of about 30 C. at least and at atmospheric pressure, in the presence of chelate organo-metallic compounds.

3. A process for oxidizing a member of the group consisting of mercaptans and mercaptides to disulfides, in which the oxidation is effected by the action of oxygen, at a temperature of about 30 C. at least and at atmospheric pressure, in the absence of chelate organo-metallic compounds, obtained by condensation of iminophenol and a metal of group VIII.

4. A process for oxidizing a member of the group consisting of mercaptans and mercaptides to disulfides, in which the oxidation is elfected by the action of a gas containing oxygen, at a temperature of about C. at least and at atmospheric pressure, in the presence of chelate organo-metallic compounds, obtained by condensation of irninophenol and a metal of group VIII.

5. A process for sweetening petroleum distillate hydrocarbons, in which they are treated with a gas consisting essentially of oxygen, at a temperature of about 30 C. at least and at atmospheric pressure, in the presence of chelate organo-metallic compounds.

6. A process for sweetening petroleum distillate hydrocarbons, in which they are treated with a gas consisting essentially of oxygen, at a temperature of about 30 C. at least and at atmospheric pressure, in the presence of chelate organo-metallic compounds, obtained by condensation of an iminophenol and a metal of group VIII.

References Cited in the file of this patent UNITED STATES PATENTS 2,651,595 Moulthrop Sept. 8, 1953 2,659,691 Gislon et al Nov. 17, 1953 2,744,854 Urban May 8, 1956 2,823,173 Gislon et al. Feb. 11, 1958 UNITED STATES PATENT OFFICE CERTIFICATE OF CORRECTION Patent No, 2,918,426 December 22, 1959 Joseph Quiquerez et al It is hereby certified that error appears in the printed specification of the above numbered patent requiring correction and that the said Letters Patent should read as corrected below.

Column 5, line 28, for "in the absence" read in the presence Signed and sealed this 24th day of May 1960 (SEAL) Attest:

KARL AXLINE ROBERT C. WATSON .Attesting Oficer Commissioner of Patents 

1. A PROCESS FOR OXIDIZING A MEMBER OF THE GROUP CONSISTING OF MERCAPTANS AND MERCAPTIDES TO DISULFIDES IN WHICH THE OXIDATION IS EFFECTED BY THE ACTION OF OXYGEN, AT A TEMPERATURE OF ABOUT 30*C. AT LEAST AND AT ATMOSPHERIC PRESSURE, IN THE PRESENCE OF CHELATE ORGANO-METALLIC COMPOUNDS. 